In the general population, the use of stamps rather than business reply postage significantly improves response rates in mail surveys.

Among physicians, however, a smaller effect might be anticipated due to their greater sophistication.

An experiment was conducted to test the hypothesis that stamps would improve response rates and lower costs in a physician survey that included intensive follow up.

In 1989, 380 physicians who reported providing primary care were surveyed.

The protocol included two mailings, a postcard reminder, and two telephone reminders.

Physicians were randomly assigned to receive a return envelope with a first-class stamp or an envelope that had been preprinted « business reply mail » in the first and second mailings.